Your guide to spotting the space station

Viewing tips
Some passes are superior to others. If the station is not predicted to get much higher than 20 degrees above your local horizon, odds are that it will not get much brighter than a moderately bright star (10 degrees is roughly equal to the width of your fist held at arm's length). In addition, with such low passes, the station will likely be visible for only a minute or two. Conversely, those passes that are higher in the sky — especially those above 45 degrees — will last longer and will be noticeably brighter.

The very best viewing circumstances are those that take the station on a high arc across the sky about 45 to 60 minutes after sunset, or 45 to 60 minutes before sunrise. In such cases, you'll have it in your sky upwards to four or five minutes. It will likely get very bright — perhaps even briefly "flare" in brilliance — and there will be little or no chance of it encountering Earth's shadow.

While the station looks like a moving star to the unaided eye, those who have been able to train a telescope on it have actually been able to see and even photograph its T-shape as it whizzed across their field of view. Some have actually been able to track the station with their scope by moving it along the projected path. Those who have gotten a good glimpse describe the body of the space station as a brilliant white, while the solar panels appear a coppery red.

For the upcoming series of evening and morning passes, take note of the fact that, for those occurring in the evening, the station will usually start out rather dim, then tend to grow in brightness as it moves across the sky. In contrast, for the morning passes, the station will already be quite bright when it first appears and will tend to fade somewhat toward the end of its predicted pass. This is due to the change in the angle of sunlight hitting the vehicle.

Lastly, remember that in certain cases, the station will either quickly disappear when it slips into Earth's shadow (during evening passes) or quite suddenly appear when it slips out of Earth's shadow (during morning passes). This becomes increasingly more likely for those predicted passes that take place more than 90 minutes after sunset or more than 90 minutes before sunrise.

When and where to look
So what is the viewing schedule for your particular hometown? You can easily find out by visiting one of these three popular web sites:

• Chris Peat's Heavens Above
• NASA's SkyWatch

Each will ask for your zip code or city, and respond with a list of suggested spotting times. Predictions computed a few days ahead of time are usually accurate to within about a minute. However, they can change due to the slow decay of the space station's orbit and periodic reboosts to higher altitudes, so check frequently for updates.

Joe Rao serves as an instructor and guest lecturer at New York's Hayden Planetarium. He writes about astronomy for The New York Times and other publications, and he is also an on-camera meteorologist for News 12 Westchester, New York.

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